I saw the movie before I read the book, but don't say "shame, shame, shame, shame" yet, because the first time I saw the movie I was only like five. I did not know Ella Enchanted was a book; I just thought it was a very good, fun movie.
I finally read the book, after loaning it to my cousin. I got the book back on Valentine's Day. My cousin told me that she read the book THREE times before she returned it to me! I was like, "This must be good! Now I have to read it." I read the book in three days. Now Ella Enchanted is one of my favorite books (in the top 5!).
Ella Enchanted is a Cinderella re-telling, but this book is not much like Cinderella at all. Similarities to the Cinderealla story: glass slippers, Prince Charming, castle, Evil Step-mom, two step-sisters, forced to serve her step-family, dead mother, Fairy God-mother, medieval setting, and the Prince throws a ball (actually three in Ella Enchanted). So, when Ella is born, she gets a gift/curse from a fairy named Lucinda. The gift is obedience. Ella has to do what anybody tells her, even if they tell her to kill herself! The book is about the fantastical kingdom in which Ella lives, where ogres, fairies, giants, and elves live, along with humans. When Ella's Moms dies, that's when the real trouble starts. She gets sent off to Finishing School, along with Hattie and Olive (who eventually become her step-sisters). Hattie figures out Ella's secret on the way to school, and uses the knowledge to torment her. The Prince falls in love with Ella at first site, at her mother's funeral. He does not profess his undying love for her until about 2/3 of the way through the book. Ella is afraid to marry the Prince, because she is afraid of someone learning her secret, and using that to control her to kill the Prince, or ruin the kingdom.
And NOW for Book VERSUS Movie!
Okay, the movie characters have the same names and personalities as the book characters, BUT that is almost where the comparison ends. Ella doesn't go to Finishing School in the movie, she's in college. She meets Hattie and Olive when her Dad marries their Mom (they don't get married in the book until WAY later in the story). In the movie there is a whole gaining the throne conspiracy that doesn't exist in the book. There is no Uncle to Prince Charming mentioned in the book. They make the orges too nice in the movie. The elves are not portrayed correctly. The giants appear a little too giant in the movie, but otherwise they are okay. Ella never gets thrown into prison for trying to kill the Prince in the book. There is no singing in the book, but that is one of the fun things about the movie. I really enjoy the music in the movie. Her Fairy God-mother in the movie is young, hip, and not very good a magic; in the book, she is old and gray and AWESOME at magic. The elves aren't forced to perform in the book, nor is Slannen the elf in the book at all. In the movie, the Prince has to keep rescuing her from disaster; in the book, she rescues herself.
All that said, if you can enjoy book and movie as separate entities, I recommend them both.